[devtools] Enables emacsy shortcuts for editor

This patch adds the emacsy shortcuts to the editor again.

Bug: chromium:983874
Change-Id: I8423fad0b0fde6ac83487189092edc8f9c66c095
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1806737Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Jan Scheffler <janscheffler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697510}

third_party/blink/renderer/devtools/front_end/text_editor/CodeMirrorTextEditor.js

@@ -129,6 +129,8 @@ TextEditor.CodeMirrorTextEditor = class extends UI.VBox {
       'Ctrl-D': 'delCharAfter',
       'Ctrl-K': 'killLine',
       'Ctrl-T': 'transposeChars',
+      'Ctrl-P': 'goLineUp',
+      'Ctrl-N': 'goLineDown',
       'Shift-Ctrl-Left': 'selectCamelLeft',
       'Shift-Ctrl-Right': 'selectCamelRight',
       'Cmd-Left': 'goLineStartSmart',